1. Field of the Invention
The present invention relates in general to seat belt retractors for use in a seat belt system installed in a motor vehicle, and more particularly to seat belt retractors of an emergency locking type which arrests the drawing of the seat belt therefrom upon sensing abnormal deceleration due to a vehicle collision or the like. More specifically, the present invention is concerned with the emergency locking type retractors which are constructed to produce less noise during their use.
2. Description of the Prior Art
In order to clarify the task of the present invention, a typical emergency locking type seat belt system will be described with an aid of FIG. 8 which shows a conventional emergency locking type retractor.
The seat belt system comprises generally a seat belt proper, a through ring with a tongue, an emergency locking type retractor and a belt anchor with a buckle. The seat belt proper extends upward from a lower outside portion of a vehicle cabin, turns back at a belt holder fixed to a higher outside portion of the cabin and extends downward to be retracted by the retractor which is mounted to the lower outside portion of the cabin. The through ring has the seat belt proper slidably passed therethrough. The belt anchor is mounted to a lower inside portion of the vehicle cabin. When the tongue of the through ring is brought into engagement with the buckle of the belt anchor, a so-called "three point restraining condition" is assumed by the seat belt system.
As is seen from FIG. 8, the emergency locking type retractor comprises a housing 29 fixed to the vehicle body, a belt retracting shaft 100 rotatably disposed in the housing 29 and having the seat belt proper wound thereabout, a coil spring (not shown) for biasing the shaft 100 in a direction to retract the seat belt proper, and a locking device which locks the belt retracting shaft 100 upon sensing abnormal deceleration of the vehicle.
As shown in the drawing, the locking device comprises a ratchet wheel 36 which is coaxially secured to the belt retracting shaft 100 to rotate therewith. Teeth of the ratchet wheel 36 are denoted by numerals 37. Located near the ratchet wheel 36 is a stand-man holder 30 which is tightly secured to the housing 29 through a bracket 11. The stand-man holder 30 has a small recess 31 at its bottom. A stand-man 32 (or weight) is loosely received in the holder 30 in such a manner that a lower projection 33 of the stand-man 32 is put in the small recess 31. The stand-man 32 has a tapered recess at a head portion. Between the ratchet wheel 36 and the stand-man 32, there is arranged a bent lever 34 which is pivotally connected through a pivot pin (no numeral) to the housing 29. One arm portion of the bent lever 34 is slidably engaged with the tapered recess of the stand-man 32 and the other arm portion 35 of the same is shaped like a pawl.
Usually, the stand-man 32 stands upright as shown by the solid line. Under this condition, the pawl of the bent lever 34 is kept away from the ratchet wheel 36, and thus, the belt retracting shaft of the belt retractor is permitted to rotate in both directions.
When, due a vehicle collision or the like, abnormal deceleration is sensed by the stand-man 32, the same is inclined as shown by a phantom line. This inclination causes the bent lever 34 to assume its operative position as shown by a phantom line wherein the pawl of the bent lever 34 abuts against one of the teeth 37 of the ratchet wheel 36. Under this condition, the belt retracting shaft 100 is locked against rotation in the direction to draw the seat belt proper from the retractor.
However, due to its inherent construction, the above-mentioned emergency locking type retractor tends to produce noises during its normal use.
That is, during cruising of the vehicle, the stand-man 32 is forced to vibrate finely due to the vibration of the vehicle. The fine vibration of the stand-man 32 causes beating of the same against the stand-man holder 30 thereby generating noises. Furthermore, the vibration of the stand-man 32 induces vibration of the bent lever 34, which also causes generation of noises. These noises are amplified by the resonance effect of the housing 29 and thus they are very offensive to the ear.